Carbon Savings of Wind Likely Reduced by Ramping of Fossil Fuels to Balance Intermittency
Researchers at the U.S. Department of Energy’s Argonne National Laboratory recently performed a modeling study aimed to quantify the total effect that increases in wind energy will have on pollutant emissions from an electric power system. Although wind energy generation does not itself generate harmful emissions, wind is thought to have the potential to create a negative effect on emissions from the rest of the power grid as thermal power producers are required to adjust their output level in response to wind’s variability and unpredictability. The study, titled “Systems-Wide Emissions Implications of Increased Wind Power Penetration” is considered to be the first to utilize a model that incorporates the effects of both thermal plant start-up and cycling emissions from an electric power system with high wind penetration. Modeled off of the Illinois electric grid, the study tested how wind energy affects emissions from fossil fuel plants as startup and cycling of thermal units increase as greater quantities of wind power are added to the grid.
The study found that the ramping of conventional fuel plants to fill intermittency gaps caused by wind on the grid may in fact cancel out some of the technology’s carbon savings. The study noted that “[t]he required level of operating reserves increases as a function of the wind power capacity, as more wind power results in increasing levels of forecast uncertainty. This has implications for the efficiency and emissions from the thermal power plants, since more plants have to be committed and operate at reduced power generation levels to provide the required spinning reserves.” However, the study also found that, despite the increase in emissions related to addressing wind’s variability, the reduction in emissions during operational periods is still enough to cause a net overall decrease in total emissions. The authors of the study note that in the model, no thermal units were retired as there was an increase of wind power, and the retirement of less-efficient thermal plants is likely to lead to greater emission reductions due to wind power. Additionally, the creation and utilization of technologies relating to more efficient, flexible thermal generation are likely to lead to even greater emissions reductions in the future.
The report can be accessed directly from ACS Publications, as published in the Journal of Environmental Science & Technology, by clicking here.